depending on what you want to do, a 15psi wastegate will be fine for your application. What you need to do is run one line from the manifold to the bottom side of the wastegate actuator and run another line from the manifold through pressure regulator to the top side. Then if you have a 15psi spring you set the pressure regulator to 15psi lower than the pressure you want to start the wastegate opening. Basically you will have equal pressure on the top and bottom of the wastegate actuator until the pressure regulator starts limiting the pressure to the top side.
Here is a diagram of what I am talking about....
2012 Mega ..... many mods to come!
2003, Smarty, TST, Twins, PDR Stage 2 Head & Cam, F1 Springs & Stix, Floor-It CP3, Technicooler, Thuren 6" Suspension w/Carli Radius Arms, Thuren X-over Steering, Toyo M/T's on KMC Beadlocks, NADP Race 48re, ATS Standalone Controller, EMS Manual Hubs